Traditionally, brewing beer begins with malted barley that is milled and mixed with hot water to form a mash. During mashing, the malt starches are converted to sugars. Next, the wort that is obtained after separating the spent grain from the mash is brought to a boil. During this stage, hops are added at different times during the boil. The wort is then cooled and aerated, and brewers' yeast is added for fermentation. After fermentation the “green beer” undergoes maturation and cold storage. Usually, the last step in the brewing process is filtration, and then carbonation. Next the beer is moved to a holding tank where it stays until it is packaged in for example bottles, cans or kegs.
It has been recognised in the beer brewing industry that the production of wort in a continuous operation offers a number of advantages, including:                higher productivity and lower investment: vessels can be operated for prolonged periods of time under full load, meaning that for equal production volume smaller vessels are needed than in a batch process;        constant and better quality: process is easier to control due to possibility of adapting process parameters to local and instantaneous requirements and because steady-state-conditions are much more stable;        high hygienic standard: continuous process is operated in a closed system;        less energy: energy consumption is evenly spread, without major use peaks;        less labour: operation of continuous process requires less attention;        the possibility to recycle heat and or materials instantaneously without the use of buffers;        less standstill and cleaning: continuous process can be operated at much longer runlengths than batch processes.        
Many efforts have been made since the end of the 19th century to realise one or more of the above advantages through the development of continuous brewing processes. However, todate across the globe not more than just a couple of breweries have actually introduced continuous brewing operations such as continuous wort production and/or continuous fermentation into their factories.
Beer is normally filtered at a late stage in the production to clarify it and to remove particles that have been carried over from earlier production stages. The filtration process usually entails either pressure filtration or the use of a filter press. In either of these two methods of beer recovery, a filter aid, such as kieselguhr, is normally used. It is also possible to clarify without the use of a filter aid, e.g. by using cross-flow membrane filtration.
Also in brewing processes that utilise continuous wort production in combination with suspended yeast fermentation, in order to produce a bright beer, solids have to be removed after yeast fermentation.
WO 94/16054 describes a continuous process for producing beer in which wort is produced and fermented in a continuous fashion. This international patent application mentions the use of a centrifuge to obtain a solids free liquid medium that is further processed to reduce the alcohol content.
DE-C 42 44 595 describes a process for continuous production of beer comprising:    a. preparing a mash and heating said mash to 75-85° C. for 30-90 minutes;    b. removing spent grain from the mash in a decanter and subsequently washing with brewing water in a two-step decanter;    c. adding hop or hop extract to the hot wort and heating the wort to a temperature of 105-140° C. for 2-60 minutes at a pressure of 1.2-3.6 bar.    d. subjecting the pressurised wort to a flash evaporation; continuously removing trub in a separator and cooling the wort to fermentation temperature in a heat exchanger;    e. continuously transferring the cooled wort having an oxygen content of 0.5-3.0 mg O2/1 to fermenter in the form of a loop reactor in which the wort is continuously recirculated and which comprises a biocatalyst in which biologically active yeast has been immobilised; and    f. continuously removing liquid medium from the fermenter during fermentation; centrifuging the removed liquid to remove free yeast cells contained therein; heating the yeast-free liquid medium to 60-90° C. for 0.5-30 minutes; cooling down; recirculating a part of the cooled stream to the fermenter and a part to final filtration of the beer.It is observed in the German patent application that a significant improvement in the final filtration is achieved as a result of centrifuging off the free yeast in a centrifuge.